U.S. patent number 5,680,960 [Application Number 08/441,617] was granted by the patent office on 1997-10-28 for volumetric fluid dispensing apparatus.
Invention is credited to James V. Curcio, Denis E. Keyes, John R. Randall.
United States Patent |
5,680,960 |
Keyes , et al. |
October 28, 1997 |
Volumetric fluid dispensing apparatus
Abstract
A fluid dispensing apparatus includes a fluid reservoir
comprising a flexible bag-like enclosure. The fluid reservoir
includes a discharge valve connected to a fluid output for
dispensing fluid from said fluid reservoir. An electronic
controller selectively opens and closes the discharge valve to
dispense a predetermined volume of fluid from said fluid reservoir.
The fluid reservoir is flexible so that it expands and contracts to
maintain the internal pressure of the fluid reservoir constant. In
an alternate embodiment, the fluid reservoir has a rigid wall and
is provided with an external bladder which expands and contracts to
maintain the internal pressure of the fluid reservoir constant. The
fluid dispensing apparatus can be configured either as a volumetric
filler or as a time pressure filler.
Inventors: |
Keyes; Denis E. (Rocky Hill,
NJ), Randall; John R. (Freehold, NJ), Curcio; James
V. (South Plainfield, NJ) |
Family
ID: |
46250368 |
Appl.
No.: |
08/441,617 |
Filed: |
May 15, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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225803 |
Apr 11, 1994 |
5480063 |
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26878 |
Mar 5, 1993 |
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Current U.S.
Class: |
222/64; 137/563;
222/318 |
Current CPC
Class: |
G01F
11/284 (20130101); G01F 13/006 (20130101); Y10T
137/85954 (20150401) |
Current International
Class: |
G01F
11/28 (20060101); G01F 13/00 (20060101); G01F
11/00 (20060101); B67D 005/08 () |
Field of
Search: |
;222/64,67,639,386.5,212,215 ;141/198 ;137/139,558,563,396 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kashnikow; Andres
Assistant Examiner: Douglas; Lisa Ann
Attorney, Agent or Firm: Rhodes, Coats & Bennett,
L.L.P.
Parent Case Text
This is a continuation-in-part of U.S. Application Ser. No.
08/225,803 filed Apr. 11, 1994, now U.S. Pat. No. 5,480,063, which
is a continuation-in-part of U.S. application Ser. No. 08/026,878
filed on Mar. 5, 1993, now abandoned entitled A Volumetric Fluid
Dispensing Apparatus.
Claims
What is claimed is:
1. A fluid dispensing apparatus for dispensing a predetermined
volume of fluid comprising:
a) a pliable fluid reservoir which expands and contracts to
maintain the internal pressure in said fluid reservoir constant,
said fluid reservoir having a fluid input connected to a fluid
supply;
b) a fluid output in said fluid reservoir for dispensing fluid from
said fluid reservoir;
c) a discharge valve connected to said fluid output for dispensing
fluid from said fluid reservoir when said valve is opened; and
d) an electronic controller for selectively opening and closing the
discharge valve to dispense a predetermined volume of fluid from
said fluid reservoir.
2. The fluid dispersing apparatus of claim 1 further including a
fluid level regulating means for maintaining the fluid level in
said fluid reservoir at a predetermined level.
3. The fluid dispensing apparatus of claim 2 wherein the fluid
level regulating means includes a measuring tube forming a closed
circuit with said fluid reservoir, a fluid level sensor disposed
along said measuring tube for detecting the level of said fluid in
said measuring tube, and control means responsive to the state of
the fluid level sensor for selectively opening and closing a supply
valve connected to said fluid input to regulate the flow of fluid
from said fluid supply into said fluid reservoir.
4. The fluid dispensing apparatus of claim 3 wherein the fluid
level sensor is external to said measuring tube.
5. The fluid dispensing apparatus of claim 4 wherein the fluid
level sensor is a photo-optic sensor.
6. The fluid dispensing apparatus of claim 5 including two level
sensors disposed along said measuring tube defining, respectively,
the upper and lower limits of the fluid level in said fluid
reservoir.
7. The fluid dispensing apparatus of claim 1 further including a
fill tube forming a closed loop with said fluid reservoir, said
fill tube being connected at one end to said fluid output, a fill
valve disposed in the closed loop formed by the fill tube for
controlling the flow of fluid into the fill tube, sensing means for
detecting the level of the fluid in the fill tube, and a drain line
connected to the fill tube, said drain valve being disposed in said
drain line.
8. The fluid dispensing apparatus of claim 7 wherein the sensing
means comprises a first optical sensor for detecting when the fill
tube is filled to a predetermined level and a second optical sensor
for detecting when the fluid level in the fill tube drops to a
second predetermined level which is lower than the first
predetermined level, wherein the controller is responsive to the
state of said first optical sensor to open said drain valve and to
the state of said second fluid level sensor to close said drain
valve.
9. The fluid dispensing apparatus of claim 7 wherein the sensing
means includes a meniscus sensor for continuously measuring the
height of the meniscus in the fill tube as the fluid is dispensed;
and wherein the controller is operative to continuously calculate
the amount of fluid dispensed based on the measured height of the
meniscus and to close the discharge valve when the calculated
volume of the fluid dispensed equals the predetermined fill
volume.
10. The fluid dispensing apparatus of claim 1 wherein the
controller is operative to open the discharge valve for a
predetermined time period to dispense a predetermined volume of
fluid.
11. The fluid dispensing apparatus of claim 1 further including a
clarification filter connected to the input of said fluid
reservoir.
12. The fluid dispensing apparatus of claim 1 further including a
rigid shell housing said pliable fluid reservoir.
13. The fluid dispensing apparatus of claim 12 wherein said fluid
reservoir is removable from said rigid shell.
14. A fluid dispensing apparatus for dispensing a predetermined
volume of fluid comprising:
a) a fluid reservoir housing a fluid input connected to a fluid
supply;
b) an external bladder connected to an upper portion of said fluid
reservoir which expands and contracts to maintain the internal
pressure within said fluid reservoir constant;
c) a fluid output in said fluid reservoir for dispensing fluid from
said reservoir;
d) a discharge valve connected to said fluid output for selectively
dispensing fluid from said fluid reservoir when said discharge
valve is open; and
e) an electronic controller operatively connected to said discharge
valve for selectively opening and closing said discharge valve to
dispense a predetermined volume of fluid from said fluid
reservoir.
15. The fluid dispensing apparatus of claim 14 further including a
fluid level regulating means for maintaining the fluid level in
said fluid reservoir at a predetermined level.
16. The fluid dispensing apparatus of claim 15 wherein the fluid
level regulating means includes a measuring tube forming a closed
circuit with said fluid reservoir, a fluid level sensor disposed
along said measuring tube for detecting the level of said fluid in
said measuring tube, and control means responsive to the state of
the fluid level sensor for selectively opening and closing a supply
valve connected to said fluid input to regulate the flow of fluid
from said fluid supply into said fluid reservoir.
17. The fluid dispensing apparatus of claim 16 wherein the fluid
level sensor is external to said measuring tube.
18. The fluid dispensing apparatus of claim 17 wherein the fluid
level sensor is a photo-optic sensor.
19. The fluid dispensing apparatus of claim 16 including two level
sensors disposed along said measuring tube defining, respectively,
the upper and lower limits of the fluid level in said fluid
reservoir.
20. The fluid dispensing apparatus of claim 14 further including a
fill tube forming a closed loop with said fluid reservoir, said
fill tube being connected at one end to said fluid output, a fill
valve disposed in the closed loop formed by the fill tube for
controlling the flow of fluid into the fill tube, sensing means for
detecting the level of the fluid in the fill tube, and a drain line
connected to the fill tube, said drain valve being disposed in said
drain line.
21. The fluid dispensing apparatus of claim 20 wherein the sensing
means comprises a first optical sensor for detecting when the fill
tube is filled to a predetermined level and a second optical level
sensor for detecting when the fluid level in the fill tube drops to
a second predetermined level which is lower than the first
predetermined level, wherein the controller is responsive to the
state of said first optical sensor to open said drain valve and to
the state of said second optical sensor to close said drain
valve.
22. The fluid dispensing apparatus of claim 20 wherein the sensing
means includes a meniscus sensor for continuously measuring the
height of the meniscus in the fill tube as the fluid is dispensed;
and wherein the controller is operative to continuously calculate
the amount of fluid dispensed based on the measured height of the
meniscus and to close the discharge valve when the calculated
volume of the fluid dispensed equals the predetermined fill
volume.
23. The fluid dispensing apparatus of claim 14 wherein the
controller is operative to open the discharge valve for a
predetermined time period to dispense a predetermined volume of
fluid.
24. The fluid dispensing apparatus of claim 14 further including a
clarification filter connected to the input of said fluid
reservoir.
25. A fluid dispensing apparatus for dispensing a predetermined
volume of fluid comprising:
a) a fluid reservoir having a fluid input connected to a fluid
supply by a fluid supply line;
b) a supply valve disposed in said fluid supply line;
c) a fluid output in said fluid reservoir for dispensing fluid from
said fluid reservoir;
d) fluid level regulating means for maintaining a predetermined
fluid level in said fluid reservoir, said fluid level regulating
means including:
i) a measuring tube forming a closed loop on said fluid reservoir,
said measuring tube having a first end connected to the fluid
reservoir below said predetermined fluid level, and a second end
connected to said fluid reservoir above said predetermined fluid
level;
ii) a fluid level sensor disposed along said measuring tube between
said first and second ends for detecting the level of fluid in said
measuring tube; and
iii) a controller for said supply valve which causes said supply
valve to open when the fluid level in said measuring tube falls
below said fluid level sensor;
e) a discharge valve connected to said fluid output for dispensing
fluid from said fluid reservoir when said valve is open; and
f) an electronic controller for selectively opening and closing the
discharge valve to dispense a predetermined volume of fluid from
said fluid reservoir.
26. The fluid dispensing apparatus of claim 25 wherein the fluid
level sensor is external to said measuring tube.
27. The fluid dispensing apparatus of claim 26 wherein the fluid
level sensor is a photo-optic sensor.
28. The fluid dispensing apparatus of claim 25 further including a
fill tube forming a closed loop with said fluid reservoir, said
fill tube being connected at one end to said fluid output, a fill
valve disposed in the fill tube for controlling the flow of fluid
into the fill tube, sensing means for detecting the level of fluid
in the fill tube, and a drain line connected to the fill tube, said
drain valve being disposed in said drain line.
29. The fluid dispensing apparatus of claim 25 wherein the
controller is operative to open the discharge valve for a
predetermined time period to dispense a predetermined volume of
fluid.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to fluid dispensing
apparatuses, and more particularly to a volumetric fluid dispensing
apparatus having no moving parts in contact with the fluid.
Numerous types of fluid dispensing apparatuses exist for filling
bottles. One type of fluid dispensing apparatus which is in
widespread use is positive displacement fillers. Positive
displacement fillers typically include moving parts which contact
and displace the fluid being dispensed. For example, one type of
positive displacement filler uses a piston and cylinder
arrangement. In this type of positive displacement filler, the
backward movement of the piston draws fluid into the cylinder
through an inlet port and the forward movement of the piston expels
the fluid through an outlet port. Another type of positive
displacement filler uses a rotary pump to move the fluid.
Positive displacement pumps have gained widespread use in the
United States for two reasons. First, positive displacement pumps
can operate at relatively high speeds, filling as many as six
hundred bottles per minute. Additionally, positive displacement
pumps are accurate up to about .+-.0.5%.
Despite the widespread use of positive displacement fillers, they
nevertheless have several disadvantages. One disadvantage with
positive displacement fillers is that the fluid comes into contact
with moving parts. As the moving parts wear, particulate matter
enters the fluid causing particulate contamination. If severe
enough, particulate contamination can render the product unusable.
Another disadvantage with positive displacement fillers involves
the difficulty in cleaning and sterilizing the moving parts in
contact with the fluid. In positive displacement pumps, the
critical tolerances between pads, such as the piston and cylinder,
precludes effective cleaning in place. Thus, the user must
disassemble the apparatus for cleaning and sterilization. This
process is not only time consuming, but may result in biological
contamination of the pads when they are handled by the mechanic
during reassembly.
Another type of fluid dispensing apparatus is the time/pressure
filler. Generally speaking, the time/pressure filler includes a
fluid reservoir which is maintained under a relatively constant
pressure. The fluid is dispensed from the reservoir through a
compressible line. Fluid flow is shut off by a pinch type valve
which squeezes and collapses the discharge line. A pre-determined
volume of fluid is dispensed by opening the discharge line for a
pre-determined period of time and then closing the line. If the
pressure within the fluid reservoir is maintained constant, an
equal amount of fluid should be dispensed each time the cycle is
repeated. However, time/pressure fillers do not work as well in
practice as they do in theory.
The primary difficulty with the time/pressure filling apparatuses
is that the tubing is deformed to shut off fluid flow and does not
always return to its undeformed state immediately, particularly
when the apparatus has been sitting idle for a long period of time.
Thus, the critical orifice through which the fluid is dispensed may
vary somewhat from the fully open line. The variance in the
critical orifice will cause the fluid flow through the discharge
line to vary until the discharge line returns to its undeformed
condition. As a result, time/pressure fillers will be less accurate
during the first few filling cycles. Furthermore, it is difficult
to use clarification filters in time/pressure fillers since it also
requires a constant pressure. The pressure drop across the filter
introduces a variable which can result in inaccurate filling.
A third type of fluid dispensing apparatus is shown in U.S. Pat.
No. 5,090,594 which discloses a volumetric fluid dispensing
apparatus. The volumetric dispensing apparatus measures a
predetermined volume of fluid in a measuring cup or fill tube which
is subsequently dispensed into a receptacle. Volumetric fillers,
while slower than positive displacement fillers, are highly
accurate and avoid the problems of microbial and particulate
contamination. However, volumetric fillers, like time/pressure
fillers, depend on a relatively constant pressure. For this reason,
it is impractical to use clarification filters in volumetric
fillers since the pressure drop across the filter may result in
inaccurate filling.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention is a fluid dispensing apparatus having a
flexible fluid reservoir which expands and contracts to maintain a
constant internal pressure. The preferred embodiment of the present
invention comprises a volumetric filler such as that described in
my co-pending application, Ser. No. 08/225,803, filed Apr. 11,
1994, which is incorporated herein by reference. The volumetric
filler disclosed herein comprises a fluid reservoir for containing
the fluid to be dispensed. The fluid reservoir is connected to a
fluid source and the level of fluid within the fluid reservoir is
regulated in a side tube. A fill tube is communicatively connected
to the fluid reservoir. The fill tube forms a closed circuit with
the fluid reservoir thereby eliminating the need for venting. A
fill valve controls the flow of fluid from the fluid reservoir into
the fill tube. A discharge valve dispenses fluid from the fill tube
into a container. The fill valve and the discharge valve are
controlled by a programmable controller which is operatively
connected to a pair of level sensors disposed along the length of
the fill tube. The level sensors detect the level of fluid in the
fill tube and the distance between the sensors along with the size
of the tube determines the fill volume.
In operation, fluid is transferred from the fluid reservoir into
the fill tube by opening the fill valve. When the fluid level in
the fill tube reaches a first predetermined height, the fill valve
is closed and the discharge valve is opened to dispense the fluid
into a container. When the fluid level in the fill tube drops to a
second predetermined level, the discharge valve is closed and the
cycle is repeated.
The present invention may also be used in time pressure fillers.
This embodiment also includes a flexible fluid reservoir for
containing the fluid to be dispensed. A drain line is connected to
the output of the fluid reservoir which includes a drain valve. The
drain valve is open for a predetermined period of time to dispense
fluid from the reservoir into a receptacle. As long as the pressure
and orifice size is maintained constant, the same volume of fluid
is dispensed during each cycle.
A primary advantage of using a flexible bag-like enclosure is that
the reservoir will expand and contract to maintain a constant
internal pressure. Another advantage of using a flexible bag-like
enclosure as a fluid reservoir is disposability. The fluid
reservoir 12 can be provided with all the necessary connectors to
enable substitution of one for another. By making the fluid
reservoir 12 disposable, the present invention avoids the necessity
of cleaning and sterilizing those parts. The old reservoir can
simply be discarded and a new one installed in its place.
In another aspect of the present invention, a rigid container can
be used as a fluid reservoir in place of the flexible bag-like
enclosure. If a rigid container is used, an external bladder is
attached to the fluid reservoir which communicates with the
interior of the reservoir. The external bladder expands and
contracts to regulate the internal pressure of the fluid reservoir
in the same manner as the flexible bag-like enclosure.
In yet another aspect of the present invention, a flexible bag-like
enclosure can be disposed in a rigid housing. The housing serves as
a containment vessel for the fluid reservoir. Additionally, the
housing can be made air tight and be pressurized.
Because there are no moving parts in contact with the fluid, the
fluid dispensing apparatus of the present invention virtually
eliminates the risk of particulate contamination of the fluid.
Additionally, the fluid reservoir can be removed and replaced
between production runs thereby eliminating the costs associated
with cleaning and sterilizing. Another significant benefit is that
sterilization or clarification filters can be used with the present
invention since the flexible fluid reservoir will always operate
under constant pressure. That is, pressure drop across the filter
will not effect the operation of the filler. The reservoir itself
will expand and contract to maintain a constant pressure.
Based on the foregoing, it is a primary object of the present
invention to provide a fluid dispensing apparatus in which all
components that contact the fluid can be supplied pre-cleaned and
pre-sterilized.
Another object of the present invention is to provide a fluid
dispensing apparatus which avoids the problems of microbial and
particulate contamination.
Another object of the present invention is to provide a fluid
dispensing apparatus which can be used with sterilizing or
clarification filters without effecting the operation of the fluid
dispensing apparatus.
Yet another object of the present invention is to provide a fluid
dispensing apparatus which can accurately fill bottles and other
receptacles to within .+-.0.5% of the fill volume.
Another object of the present invention is to provide a fluid
dispensing apparatus which is capable of filling bottles having
volumes in the range of 0.1 cc to 1.0 liters or more.
Still another object of the present invention is to provide a fluid
dispensing apparatus capable of filling up to 300 bottles per
minute or at speeds comparable to piston filling for aqueous
liquids.
Another object of the present invention is to provide a fluid
dispensing apparatus which is simple in construction and reliable
in operation.
Other objects and advantages of the present invention will become
apparent and obvious from a study of the following description and
the accompanying drawings which are merely illustrative of such
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating a preferred embodiment
of the fluid-dispensing apparatus of the present invention.
FIG. 2a is a flow diagram illustrating the mode of operation of the
fluid-dispensing apparatus during a dispense cycle.
FIG. 2b is a flow diagram illustrating an alternate mode of
operation of the fluid-dispensing apparatus during the dispense
stage of the dispense cycle.
FIG. 2c is a flow diagram illustrating a second alternate mode of
operation during the dispense stage of the dispense cycle.
FIG. 3 is a schematic diagram illustrating a second embodiment of
the fluid dispensing apparatus.
FIG. 4 is a schematic diagram illustrating a third embodiment of
the fluid dispensing apparatus.
FIG. 5 is a schematic diagram illustrating a fourth embodiment of
the fluid dispensing apparatus.
FIG. 6 is a schematic diagram illustrating a fifth embodiment of
the fluid dispensing apparatus.
FIG. 7 is a schematic diagram illustrating a sixth embodiment of
the fluid dispensing apparatus.
FIG. 8 is a schematic diagram illustrating a seventh embodiment of
the fluid dispensing apparatus.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and more particularly to FIG. 1, the
dispensing apparatus of the present invention is shown therein and
indicated generally by the numeral 10. The dispensing apparatus 10
includes a fluid reservoir 12 having a fill port 14 which is
connected by a fluid supply line 16 to a fluid source 18. A
sterilization or clarification filter 17 is disposed in the fluid
supply line 16. The fluid reservoir 12 is a sealed, flexible
bag-like enclosure which expands and contracts during operation as
will be hereinafter described. The fluid supply line 16 includes a
supply valve 20 which is activated by solenoid 21. To maintain the
fluid level in the fluid reservoir 12 at a predetermined level, a
fluid level sensor 22 is positioned along a side tube 23. One end
of the measuring tube 23 is connected to a lower portion of the
fluid reservoir 12 while the opposite end is connected to an upper
portion of the fluid reservoir 12 (called the "head space") as
shown in FIG. 1. The level of fluid in the measuring tube 23 is
equal to the level of fluid in the fluid reservoir 12. The fluid
level sensor 22 snaps around the outside of the side tube 23 and
its vertical position determines the fluid level in the fluid
reservoir. A programmable controller (not shown) is operatively
connected to the fluid level sensor 22 and solenoid 21. When the
fluid level in the fluid reservoir 12 drops below the level of the
sensor 22, the programmable controller opens supply valve 20 to
introduce more fluid into the fluid reservoir 12. Thus, the level
of fluid in the fluid reservoir will always remain constant. It
will be appreciated also that multiple sensors 22 could be used
along with side to define upper and lower limits.
The fluid reservoir 12 includes a drain port 24 which is connected
to a fill tube 36. The fill tube 36 is connected at one end to the
drain port 24 in a lower portion of the fluid reservoir 12. The
opposite end of the fill tube 36 connects to a vent 38 in the upper
portion of the fluid reservoir 12. Thus, the fill tube 36 forms a
closed loop with the fluid reservoir 12. A fill valve 30 is
disposed in the closed loop for controlling the flow of fluid from
the fill reservoir 12 to the fill tube 36. The fill valve 30 is
controlled by solenoid 31 which is connected to the programmable
controller.
A drain line 26 connects to the fill tube 36 for dispensing fluid
from the fill tube 36 into a container. Drain line 26 includes a
drain valve 28 for dispensing fluid as will be hereinafter
described. The drain valve 28 is controlled by a solenoid 29 which
is activated by the programmable controller.
A pair of optical-level sensors 32 and 34 are disposed along the
fill tube 36. Both sensors 32 and 34 must be disposed below the
level of the fluid in the fluid reservoir 12. The upper level
sensor 34 defines an upper level of fluid in the fill tube 36. The
lower level sensor 32 defines a lower level of fluid. The volume of
fluid dispensed is determined by the distance between the upper and
lower level sensors 32 and 34 and the diameter of the fill tube 36.
Both sensors 32 and 34 are connected to the programmable
controller.
A meniscus sensor 42 may be included in addition to or in place of
level sensors 32 and 34. If a meniscus sensor 42 is used, it is
located in a tube extension 40 in the fill-tube loop 36. The
meniscus sensor 42 is a laser-type sensor which measures the height
of the meniscus in the fill tube 36. The output of the meniscus
sensor 42 is transmitted to the programmable controller which uses
the information to improve the accuracy of the fill volume.
The programmable controller controls the operation of the fluid
dispensing apparatus 10 as shown in FIG. 2A. The dispensing cycle
includes a filling stage during which the fill tube 36 is filled
with fluid, and a dispense stage in which the fluid is dispensed
into a container. At the start of a filling stage, the fluid level
in the fill tube 36 is at the level of the first optical sensor 32.
Drain valve 28 is closed and fill valve 30 is open so that fluid
from the fluid reservoir 12 flows into the fill tube 36. The fluid
rises in the fill tube 36 until it reaches the level of the second
optical sensor 34. Once the fluid reaches this level, the
programmable controller closes the fill valve 30 and opens the
drain valve 28. This marks the end of the filling stage and the
beginning of the dispense stage. The fluid in the fill tube 36 then
drains through the drain line 26 into a container. The fluid
recedes in the fill tube 36 until it reaches the level of the first
optical sensor 32 at which time the drain valve 28 closes and the
cycle repeats.
During the dispensing stage of the cycle, variations in the height
of the meniscus may cause some deviation in the volume of fluid
dispensed. The meniscus sensor 42 may be used to reject
out-of-range fill volumes or to compensate for variations in the
height of the meniscus. At the beginning of the dispense stage of
the cycle, the height of the meniscus in the fill tube 36 is
measured by sensor 42 and stored in the programmable controller's
memory. Discharge valve 28 opens until the fluid drops to the level
of sensor 32. When the sensor 32 detects the receding meniscus, the
discharge valve 28 is closed completing the dispensing cycle. After
the discharge valve closes, the final position of the meniscus is
determined by the sensor 42 allowing the programmable controller to
calculate the actual volume dispensed. By calculating the actual
volume dispensed, out-of-range fill volumes can be rejected on line
as they occur.
By knowing the height of the upper meniscus before the dispense
stage of the cycle begins, the programmable controller can also
delay the closing of the drain valve 28 after sensor 32 sees the
receding meniscus if a smaller than normal upper meniscus has been
detected. This will compensate for an otherwise, lower than normal
fill volume. By measuring the position of the meniscus at the
beginning of the dispense stage and then determining how long it
takes to reach the position of sensor 32, a delay can be calculated
by the controller which will enable drain valve 28 to remain open
an additional amount of time needed to yield the correct fill
volume.
The meniscus sensor 42 can also be used to replace the lower sensor
32. FIGS. 2B and 2C show alternate modes of operation during the
dispensing stage which eliminate the need for level sensor 32.
Referring now to FIG. 2B, the dispense stage begins by measuring
the height of the meniscus in the fill tube 36 and opening the
discharge valve 28. While fluid is being dispensed, the controller
continuously monitors the height of the meniscus in a manner
similar to Doplar radar as it recedes and calculates the volume of
fluid dispensed. When the calculated value of the fluid dispensed
equals a predetermined fill volume, which is set by the user, the
discharge valve 28 is closed. The dispensing cycle will then be
repeated indefinitely until the apparatus is turned off.
In a third mode of operation, shown in FIG. 2C, a first
predetermined volume (V) is dispensed which is equal to
approximately 95% of the desired fill volume. After the first
predetermined volume (V.sub.1) is dispensed, the controller
calculates the amount actually dispensed based on the position of
the meniscus and determines the remaining volume (V.sub.R) needed
to equal the total fill volume. The discharge valve 28 is reopened
to dispense the remaining volume (V.sub.R) which is approximately
5% of the total fill volume. While dispensing the remaining 5%, the
height of the meniscus is continuously measured and the volume
dispensed (V.sub.2) is calculated. With the amount dispensed
(V.sub.2) equals the remaining volume calculated by the controller,
the discharge valve 28 is closed. Alternately, the remaining 5%
could be dispensed by opening the discharge valve 28 for a
predetermined time period which is calculated by the controller
based on the pressure in the fluid reservoir 12 and the specific
gravity of the fluid. This alternate method for dispensing the
remaining 5% is shown by dotted lines in FIG. 2C. The advantage of
this approach is that it greatly reduces the amount of error for
extremely accurate filling. The disadvantage is that it increases
the time needed to dispense a given volume of fluid.
The present invention solves the problem experienced in the past
with using clarification filters in volumetric filters. Because the
fluid reservoir 12 is flexible, it can expand and contract during
use to maintain the internal pressure of the fluid reservoir 12
constant. No external pressure source is required. The fluid
dispensing apparatus 10 will be self-regulated and will maintain an
internal pressure equal to the external pressure, which will
ordinarily be atmospheric pressure. Because the fluid dispensing
apparatus is self-regulating, the pressure drop across the
clarification filter will not effect its operation.
Referring now to FIG. 3, an alternate embodiment of the present
invention is shown. The embodiment shown in FIG. 3 differs from the
first embodiment only in that the fluid reservoir 12 comprises a
rigid enclosure whereas the fluid reservoir 12 in the first
embodiment comprises a flexible, bag-like enclosure. A flexible
bladder 25 communicates with the interior of the fluid reservoir
12. The flexible bladder 25 serves to regulate the pressure in the
fluid reservoir 12.
FIG. 4 illustrates a third embodiment similar to the embodiment in
FIG. 1. However, the embodiment shown in FIG. 4 is configured for
time-pressure filling. The fill tube 36 of the first embodiment and
its associated sensors 32 and 34 are eliminated. In its place, a
timer 27 is connected to the solenoid 29 which controls the drain
valve 28. When a bottle is positioned beneath the drain line 26,
the drain valve 28 is opened and the fluid is dispensed from the
fluid reservoir 12 into the bottle. After a predetermined period of
time has elapsed, the timer 27 causes the drain valve 28 to close
to stop the flow of fluid from the fluid reservoir 12. As in the
first embodiment, this embodiment can be used with a clarification
filter 17 since the fluid reservoir 12 will expand and contract to
maintain the pressure constant. Thus, the pressure drop across the
clarification filter 17 does not interfere with the operation of
the fluid dispensing apparatus 10.
FIG. 5 shows a fourth embodiment of the present invention which is
similar to the embodiment shown in FIG. 3. The embodiment shown in
FIG. 5 is also configured for time-pressure filling. However, the
fluid reservoir 12 has a rigid wall and is provided with a bladder
25 for regulating pressure within the fluid reservoir 12.
FIG. 6 illustrates a fifth embodiment of the present invention. The
embodiment shown in FIG. 6 is configured as a volumetric filler and
is similar to the embodiment shown in FIG. 1. However, the
embodiment shown in FIG. 6 includes a housing 40 which encloses the
fluid reservoir 12. It is understood that the fluid reservoir 12 is
of the flexible type. The housing 40 is constructed in two halves
extending lengthwise to allow easy insertion and removal of the
fluid reservoir 12 from the housing 40.
The housing 40 may serve simply as a containment vessel for the
fluid reservoir, or may itself be pressurized. If the housing 40 is
used as a containment vessel, as shown in FIG. 6, a small vent
should be placed in the housing 40 to allow for expansion of the
fluid reservoir 12. Alternatively, the housing 40 could be
constructed of a porous material.
If the housing 40 is pressurized, as shown in FIG. 7, air tight
seals should be used between the housing 40 and the fluid reservoir
at fill port 14, around the side tube 23, at vent 38, and at drain
port 24. The fluid reservoir 12 may also be pressurized as shown in
FIG. 8. Both the housing 40 and reservoir 12 can be pressurized at
the same time. If the housing 40 or the fluid reservoir 12 is
pressurized, the clarification filter 17 should preferably be
removed to avoid errors resulting from the pressure drop across the
filter.
Based on the foregoing, it is apparent that the present invention
provides a fluid dispensing apparatus in which all of the
components which come in contact with the fluid being dispensed can
be pre-cleaned and sterilized. These components can be easily and
quickly replaced thereby eliminating down time while components are
being cleaned. The present invention also may be used with
clarification filters without the errors associated with prior art
devices.
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